An armor-penetrating projectile of great length/diameter ratio and density is known which has a front part formed as an outer substantially cylindrically tubular member centered on an axis and having an axially throughgoing bore defined by an inner surface and an axially elongated inner member of greater strength and elasticity than the outer member extending axially through the bore the full length of the outer member.
As described in German patent document No. 2,743,732 (which corresponds to coassigned U.S. patent application Ser. No. 949,067, filed Sept. 15, 1978, which has been abandoned in favor of coassigned continuation-in-part application Ser. No. 412,794, filed Aug. 23, 1982) the front region of such a penetrator is formed of a stack of heavy rings and the inner member is formed as a bolt screwed at its axially rear end into the front of a main penetrator body. The bolt is formed level with each joint between two adjacent rings with a weakening or break groove. Thus when the penetrator first impinges the armored target the rings will break apart in controlled manner, and the mass of the main body behind them will increase the impact.
Unfortunately the violence of firing such a shell frequently is too great for the main penetrator to withstand, so it breaks up in flight. Its inertia is therefore lost to the front portion. Without the extra mass of the main body the shell is ineffective against new laminated armor.
In order to overcome this breaking-up problem it is standard to surround the heavy sintered-metal penetrator with a steel casing. In order to secure the casing at the rear to the charge carrier it is necessary to thread it, and such threads can only be cut in a relatively thick-walled casing. As a result this casing takes up a considerable portion of the volume of the shell, taking the place of denser and more effective armor-piercing material.